In a factorial experiment, a study has been made of the effects of small amounts of alloying elements and processing variables on the magnetic properties of the 50% nickel‐iron alloy. The composition variables were: three levels of manganese, two of silicon, two of sulfur, and two of oxygen. The processing variables were: hot rolling at two temperature levels, annealing or not annealing after hot rolling, and final annealing at six temperature levels. The ingots were processed to tape from which toroidal cores were made.The results of magnetic tests made with a constant current, flux‐reset core tester indicate that certain elements need to be added to the melt to produce a grain‐oriented alloy with satisfactory magnetic properties, and that the processing must be compatible with the additions made. The binary manganese‐oxygen addition was most beneficial. In general, hot rolling at a high temperature level was beneficial, and annealing after hot rolling was detrimental to the magnetic performance.